1. Field of the Invention
The present invention relates to a bearing device, an information recording and reproducing device, and a manufacturing method for the bearing device.
2. Description of the Related Art
There has been known an information recording and reproducing device such as a hard disk drive that causes a disk (a magnetic recording medium) to store and reproduce various kinds of information. In general, the information recording and reproducing device includes a head gimbal assembly including a slider for recording a signal in and reproducing a signal from the disk and an arm (a turning member), to the distal end side of which the head gimbal assembly is attached. The arm is enabled to turn by a bearing device provided on the proximal end side. By turning the arm, it is possible to move the slider to a predetermined position of the disk and perform recording and reproduction of a signal.
In general, the bearing device includes a shaft and a pair of roller bearings inserted over the shaft and disposed side by side in the axial direction of the shaft. The pair of roller bearings respectively includes inner rings fixed to the shaft, outer rings surrounding the inner rings, and pluralities of rolling elements disposed between the inner rings and the outer rings (see, for example, JP-A-2009-191895 (Patent Literature 1)).
In such a bearing device, inner gaps between the outer and inner rings and the rolling elements are eliminated and rigidity of the roller bearings is increased by applying preloads in directions in which the inner rings of the pair of roller bearings are brought close to each other. In order to dispose the roller bearings in a state in which the preloads are applied thereto, it is necessary to dispose the pair of roller bearings side by side in the axial direction and fix the inner rings to the shaft in the state in which the preloads are applied thereto.
In recent years, a reduction in the thickness of an information recording and reproducing device has been in progress. However, in the bearing device in the related art, the pair of roller bearings is disposed side by side in the axial direction in order to increase the rigidity of the roller bearings. Therefore, there is a limit in the reduction in the thickness.